In 1953, it was first recognized that ingestion of gluten, a common dietary protein present in wheat, barley and rye causes a disease, now called Celiac sprue, in sensitive individuals. Gluten is a complex mixture of glutamine- and proline-rich glutenin and prolamine molecules, that appears to be responsible for disease induction. Ingestion of such proteins by sensitive individuals produces flattening of the normally luxurious, rug-like, epithelial lining of the small intestine known to be responsible for efficient and extensive terminal digestion of peptides and other nutrients. Clinical symptoms of Celiac sprue include fatigue, chronic diarrhea, malabsorption of nutrients, weight loss, abdominal distension, anemia, as well as a substantially enhanced risk for the development of osteoporosis and intestinal malignancies (lymphoma and carcinoma). The disease has an incidence of approximately 1 in 200 in European populations.
A related disease is dermatitis herpetiformis, which is a chronic eruption of the skin characterized by clusters of intensely pruritic vesicles, papules, and urticaria-like lesions. IgA deposits occur in almost all normal-appearing and perilesional skin of individuals with the disease. Asymptomatic gluten-sensitive enteropathy is found in 75 to 90% of patients and in some of their relatives. Onset is usually gradual. Itching and burning are severe, and scratching often obscures the primary lesions with eczematization of nearby skin, leading to an erroneous diagnosis of eczema. Strict adherence to a gluten-free diet for prolonged periods may control the disease in some patients, obviating or reducing the requirement for drug therapy. Dapsone, sulfapyridine and colchicines are sometimes prescribed for relief of itching.
Celiac sprue is generally considered to be an autoimmune disease, and the antibodies found in the serum of patients support a theory of an immunological nature of the disease. Antibodies to tissue transglutaminase (tTG) and gliadin appear in almost 100% of the patients with active Celiac sprue, and the presence of such antibodies, particularly of the IgA class, has been used in diagnosis of the disease.
The large majority of patients express the HLA-DQ2 [DQ(a1*0501, b1*02)] and/or DQ8 [DQ(a1*0301, b1*0302)] molecules. It is believed that intestinal damage is caused by interactions between specific gliadin oligopeptides and the HLA-DQ2 or DQ8 antigen, which in turn induce proliferation of T lymphocytes in the sub-epithelial layers. T helper 1 cells and cytokines apparently play a major role in a local inflammatory process leading to villus atrophy of the small intestine.
At the present time, there is no approved drug therapy for the disease, and the only “treatment” is to advise patients to avoid all foods containing gluten. Although gluten withdrawal has transformed the prognosis for children and substantially improved it for adults, some people still die of the disease, mainly adults who had severe disease at the time of diagnosis. An important cause of death is lymphoreticular disease (especially intestinal lymphoma). It is not known whether a gluten-free diet diminishes this risk. Apparent clinical remission is often associated with histologic relapse that is detected only by review biopsies or by increased EMA titers.
Gluten is so widely used, for example in commercial soups, sauces, ice creams, hot dogs, and other foods, that patients need detailed lists of foodstuffs to avoid and expert advice from a dietitian familiar with celiac disease (as Celiac sprue is sometimes called). Ingesting even small amounts of gluten may prevent remission or induce relapse. Supplementary vitamins, minerals, and hematinics may also be required, depending on deficiency. A few patients respond poorly or not at all to gluten withdrawal, either because the diagnosis is incorrect or because the disease is refractory. In the latter case, oral corticosteroids (e.g., prednisone 10 to 20 mg bid) may induce response.
In view of the serious and widespread nature of Celiac sprue, improved methods of treating or ameliorating the effects of the disease are needed. Recently, a promising new approach to the treatment of the disease has been described: the use of orally ingested proteases that degrade gluten before it can exert its toxic effects in Celiac sprue and dermatitis herpetiformis patients (see U.S. Pat. Nos. 7,303,871 and 7,320,788, each of which is incorporated herein by reference). To increase the efficacy of this approach, new protease preparations with increased ability to degrade gluten, relative to currently available protease preparations, are needed. The present invention addresses such needs.